An investigation of plate-type windborne debris flight using coupled CFD–RBD models. Part I: Model development and validation

The development of a coupled computational fluid-dynamics rigid body (CFD–RBD) model is presented. The RBD model deploys rotational quaternions, which are free from the gimbal lock that is associated with Euler rotational matrix. The quaternion model means that the complex 3D spinning flight modes associated with the flight of plate-type windborne debris can be modelled robustly. This paper attempts to determine the accuracy of the CFD–RBD model by comparing the predicted trajectories from a large number of debris simulations with experimentally derived equations of best fit. Agreement is found to be good and, based on the findings, an alternative form for the dimensionless flight distance is presented, which extends the range of the experimental study to longer flight times. The predictions from the CFD–RBD model are then compared against two quasi-steady analytical debris flight models. The second model is based on modified force and moment coefficients, which are informed by the findings from the CFD–RBD model. For plates that have attained a stable, autorotational flight mode, the CFD–RBD and analytical models are in good agreement. Their predictions differ during the initial stages of flight, where the complex non-linear interactions between the plate and its wake are not captured by the analytical models.